Alarm indicating fuses provide an external signal, typically an audio alert such as buzzer, or a visual alert such as a lamp or a mechanical pin, that a circuit fault has occurred. Alarm indicating fuses are advantageous in systems where a large number of fuses are arrayed to protect various electrical circuits, or portions of circuits. Swiftly locating a circuit fault is important for the safety and operation of the system, and locating an individual circuit fault without an external fault indicator is slow and time consuming.
Alarm indicating fuses generally include a fuse element that cooperates with a fuse holder to activate a visual or audio signal when a circuit fault occurs. One type of fault indicating fuse element comprises a cartridge-type fuse element having an axially mounted pin in one head or ferrule of the fuse element. The pin extends from the fuse element when the fuse element interrupts the circuit because of a short circuit or an overcurrent condition. The pin contacts an electrical contact in the fuse holder to complete a circuit activating the fault indicator, e.g. a lamp or buzzer.
For the indicator alarm to function, the fuse element must be positioned in the fuse holder so that the end having the indicator pin is oriented with the alarm circuit contact in the fuse holder. The interrupting function itself of the fuse element is not affected by the orientation of the fuse element in the fuse holder, that is, an incorrectly oriented fuse element will succeed in interrupting a circuit in the event of a fault condition. In addition, non-indicating fuse elements of an appropriate rating can be used safely in alarm indicating fuse holders if the indicating function is relinquished.
The present invention provides a device to ensure quickly and reliably the correct orientation of an alarm indicating fuse element in a fuse holder. The device of the present invention provides both visual and mechanical means to correctly orient a fuse element in a fuse holder.
More particularly, the present invention provides an orientation ring that may be removably positioned on a fuse element and cooperates with a fuse element receiving space in a fuse holder to ensure that the fuse element is positioned in a selected orientation. An orientation ring in accordance with the present invention positioned on a fuse element creates a non-symmetrical appearance that corresponds to a non-symmetrical fuse element receiving space in a fuse holder to direct a user to orient correctly the fuse element.
The fuse element receiving space is configured to interfere with an orientation ring positioned on a fuse element which is incorrectly oriented, the receiving space preventing the fuse element holder from accepting the incorrectly oriented fuse element. Conversely, when the fuse element is correctly oriented, the fuse element receiving space accepts the fuse element and orientation ring without interference and allows the fuse element to be installed in the fuse element holder.
A fuse element holder according to the present invention does not prevent the installation of a fuse not carrying an orientation ring of the present invention. The fuse element holder of the present invention can therefore be used with non alarm indicating fuse elements if necessary.
The fuse orientation ring of the present invention is formed of a non-conducting material and does not comprise an electrically functional part of a fuse element on which the orientation ring is positioned. The orientation ring comprises an annular first portion having an inner diameter sufficient to accept therein a head, or ferrule, portion of a fuse element. A plurality of projections extend from the first portion from a plane defined by the first portion and angled toward a center of the first portion. Remote ends of the projections define a passage having an inner diameter smaller than the inner diameter of the first portion, and sufficiently large to accept therein a cylindrical body portion of a fuse element.
The fuse orientation ring of the present invention is positionable on a fuse element by inserting a head portion of the fuse element through the first portion from a side opposite the projections, and then past the projections, which deform to allow the head to pass. Once the head has passed, the projections recover their original position so that the remote ends engage a body portion of the fuse element to retain the orientation ring at a selected position on the fuse element.
Once positioned on a fuse element, the orientation ring, which has an outer diameter greater than an outer diameter of the fuse element, projects radially outward from the body of the fuse element. The fuse element holder is provided with fuse element mounting means that includes generally C-shaped fuse clips to retain the opposing head portions of the fuse element and provide electrical connection therewith to connect the fuse element in an electrical circuit.
The fuse clips are located in a fuse element receiving space that is configured to permit a fuse element carrying an orientation ring to be positioned in the mounting means in a selected orientation only. The fuse element receiving space is defined by a shoulder portion located at a selected end of the space adjacent to a fuse clip. The shoulder interferes with the orientation ring so that the head portion adjacent to an orientation ring cannot be inserted in the fuse clip mounting. At an opposing end of the receiving space, a relief gap adjacent to an opposing fuse clip provides sufficient space to accept the orientation ring and permit the head end adjacent to the orientation ring to be inserted in the fuse clip.
An incorrectly oriented fuse element may be partially received in the receiving space, wherein a head portion at the relief gap end is partially retained in the respective fuse clip, but the orientation ring interferes with the opposing end portion being positioned in the other fuse clip.
According to another aspect of the invention, the fuse element holder is positionable in a fuse housing. An aperture for receiving the fuse element holder prevents the insertion of a holder with an incorrectly oriented fuse element.
The orientation ring and the fuse element holder may include color coding to facilitate further visual means for orienting the fuse element in the fuse holder.